The present disclosure relates to a touchscreen device and a method for controlling the same.
A touchscreen device, such as a touchscreen or a touch pad, is a data input device attached to a display device so as to provide an intuitive user interface, and has recently been widely applied to various electronic devices such as cellular phones, personal digital assistants (PDA), and navigation devices. Particularly, as demand for smartphones has been recently increased, touchscreens have been increasingly employed therein, since they are able to provide users with various data input methods in a limited form factor.
Touchscreens used in portable devices may be mainly divided into resistive type touchscreens and capacitive type touchscreens, depending on the manner in which touches are sensed therein. Among these, capacitive type touchscreens have advantages of a relatively long lifespan and ease in the implementation of various types of data input and gestures therefor, and thus it has been increasingly employed. It is especially easy to implement a multi-touch interfaces with capacitive type touchscreens, as compared to resistive type touchscreens, and thus, capacitive type touchscreens are widely used in smartphones and the like.
In capacitive type touchscreens, in the case that capacitance values of capacitors provided on a touch panel are changed by a user's finger or stylus, the changed capacitance values are converted into electrical signals and in turn into digital signals, so that it may be determined whether a touch input has been made. In addition, various methods of converting capacitance values into electrical signals are also being developed. Among others, a method of using integrators is frequently used because it includes several operations of the conversion of capacitance of capacitors into voltage to be output, and thus it contains less noise than other methods in which the conversion is only performed once.
Incidentally, a touchscreen panel may be installed to be operated, like a liquid crystal display (LCD) or an organic light emitting diode (OLED). A transmitting terminal Tx and a receiving terminal Rx of an IC are connected to both panel terminals. The transmitting terminal Tx is provided to drive capacitors in the panel and the receiving terminal Rx is provided to receive signals from the capacitors to be converted into voltages. The number of channels of the receiving terminal Rx is determined depending on the size of the panel, and each of the channels has an offset. The offset may be caused for two reasons. First, the offset may be caused by deviations in capacitance values of capacitors inside the panel. Second, the offset is caused by changes in gains of integration circuits due to changes in PVT. Such an offset may lead to deterioration of linearity and accuracy.